Sliding component

ABSTRACT

In an embodiment, a sliding part is provided with a mechanism to generate dynamic pressure by means of relative sliding of a pair of sealing faces of the sliding part, which is characterized in that one sealing face is provided with a land  10  for generating dynamic pressure facing the high-pressure fluid side and a seal area  11  facing the low-pressure fluid side, wherein the land  10  and seal area  11  are positioned away from each other in the radial direction and the areas of the sealing face other than the land  10  and seal area  11  are formed lower than these areas to constitute fluid communication paths  12 . The fluid entering the grooves for generating dynamic pressure formed on the sealing face is allowed to circulate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/431,733, filed Mar. 26, 2015 now U.S. Pat. No. 9,951,873, issued Apr.24, 2018, which in turn is a U.S. National Phase under 35 U.S.C. 371 ofInternational Application No. PCT/JP2014/050402, filed Jan. 14, 2014,which claims priority to Japanese Patent Application No, 2013-005494,filed Jan. 16, 2013. The International Application was published underPCT Article 21 (2) in a language other than English.

TECHNICAL FIELD

The present invention relates to a sliding component suitable formechanical seals, bearings and other sliding areas. In particular, thepresent invention relates to a seal ring, bearing, or other slidingcomponent that must reduce friction by allowing a fluid to be presentbetween the sealing faces, while preventing the fluid from leaking outof the sealing faces.

BACKGROUND ART

The performance of a mechanical seal, which is an example of a slidingcomponent, is evaluated based on the leakage rate, wear rate, andtorque. Mechanical seals of prior arts have achieved greater performancein the form of low leakage, long life, and low torque by optimizingtheir sealing material and roughness of seal area. In recent years,however, the ever-growing awareness of environmental issues in themarket has created a demand for mechanical seals offering even higherperformance and a consequent need to develop technologies that go beyondthe scope of prior arts. One type of prior art relating to a mechanicalseal is to provide grooves 52 on a sealing face 51 of one sliding ring50 in order to obtain dynamic pressure between a pair of sliding ringsthat rotate relative to each other, as shown in FIG. 15 (refer to PatentLiterature 1, for example).

CITATION LIST Patent Literatures

Patent Literature 1: Japanese Utility Model Laid-open No. Sho 63-33027(FIGS. 4 and 5)

SUMMARY OF INVENTION Technical Problem

Under the aforementioned prior art, the grooves 52 are open to thehigh-pressure fluid side (sealed fluid side), but closed off from thelow-pressure fluid side by a land R, with each groove 52 isolated fromone another in the circumferential direction by the land R. Since thegrooves 52 have a dead-end structure as mentioned above, the fluidentering each groove 52 is poorly circulated and if impurities havemixed into the fluid, the impurities may remain as deposits 54 at adownstream end 53 of the dead end and the deposits may even circulateover the sealing face 51 to damage the sealing face 51, or accumulatingdeposits may push the sealing faces of the pair of sliding rings widerapart to cause the sealed fluid to leak.

The object of the present invention is to provide a sliding componentthat allows the fluid entering the grooves for generating dynamicpressure (hereinafter referred to as “dynamic-pressure generationgrooves”) formed on its sealing face to circulate and thereby preventthe sealing face from being damaged by impurities contained in thefluid, while also preventing deposited impurities from pushing widerapart the sealing faces of the pair of sliding rings, thereby improvingthe lifespan as well as sealing function.

SOLUTION TO PROBLEM Principles

The present invention is such that the areas other than the land forgenerating dynamic pressure facing the high-pressure fluid side and theseal area facing the low-pressure fluid side are formed one step lowerand these lower areas constitute fluid communication paths, in order toeliminate dead ends of dynamic-pressure generation grooves to allow thefluid to circulate and thereby prevent the sealing face from beingdamaged by impurities contained in the fluid, while preventing depositedimpurities from pushing wider apart the sealing faces of the pair ofsliding rings.

Means

To achieve the aforementioned object, firstly, the sliding componentproposed by the present invention is the sliding component provided witha mechanism to generate dynamic pressure by means of relative sliding ofa pair of sealing faces of the sliding component, which is characterizedin that one sealing face is provided with a land for generating dynamicpressure facing the high-pressure fluid side and a seal area facing thelow-pressure fluid side, wherein the land and seal area are positionedaway from each other in the radial direction and the areas of thesealing face other than the land and seal area are formed lower thanthese areas to constitute fluid communication paths.

According to these features, the fluid entering the fluid communicationpath extending in the radial direction, from the high-pressure fluidside, is pressurized by means of the dynamic-pressure generating actionof the land and positive pressure is generated, and consequently thespace between the sealing faces is widened and the lubrication of thesealing faces improves as a result. As this happens, impuritiescontained in the fluid circulate in the fluid communication path andeventually are discharged toward the high-pressure fluid side bycentrifugal forces, instead of damaging the sealing faces, and thereforethe life of the sliding component can be extended significantly. Inaddition, impurities do not deposit on the sealing faces to widen thespace between the sealing faces, which in turn leads to greater sealingfunction.

In addition, secondly, the sliding component proposed by the presentinvention is characterized in that, with regard to the first features,the land is provided at multiple locations at an equal pitch in thecircumferential direction.

According to these features, required dynamic pressure is generateduniformly in the circumferential direction to improve the lubrication ofthe sealing face as a whole, while allowing the impurities contained inthe fluid to be discharged without fail.

In addition, thirdly, the sliding component proposed by the presentinvention is characterized in that, with regard to the first or secondfeatures, the land has an approximately U-shaped profile and ispositioned in such a way that the top of the approximate U shape facesthe high-pressure fluid side.

According to these features, the presence of the dynamic-pressuregeneration area being elongated in the radial direction improves thelubrication and reduces the friction. Also, the fluid communication pathextending in the radial direction communicates with the fluidcommunication path extending in the circumferential direction along asmooth arc, which allows the impurities contained in the fluid to bedischarged without being stagrated in the middle and depositing. As aresult, the sealing face is not damaged and this prevents the sealingface from corroding.

In addition, fourthly, the sliding component proposed by the presentinvention is characterized in that, with regard to the first or secondfeatures, the land has a quadrilateral profile and is positioned in sucha way that one corner of the quadrilateral faces the high-pressure fluidside.

According to these features, the fluid communication path has a wideentrance facing the high-pressure fluid side and narrows toward thelow-pressure fluid side after the entrance and then widens again nearthe fluid communication path extending in the circumferential direction,and this allows the impurities contained in the fluid to be furtherdischarged.

In addition, fifthly, the sliding component proposed by the presentinvention is characterized in that, with regard to the first or secondfeatures, the land has a profile corresponding to multiple circlesarranged in the radial direction.

According to these features, a seal structure suitable for thrustbearings can be provided and the impurities contained in the fluid canbe discharged efficiently toward the high-pressure fluid side.

In addition, sixthly, the sliding component proposed by the presentinvention is characterized in that, with regard to any of the firstthrough fifth features, the fluid communication path is provided with aspiral groove for discharging fluid.

According to these features, the fluid entering the fluid communicationpath is biased toward the high-pressure fluid side by the spiral groovefor discharging fluid, and therefore the impurities contained in thefluid are further discharged toward the high-pressure fluid side bycentrifugal forces and the biasing force from the spiral groove.

In addition, seventhly, the sliding component proposed by the presentinvention is characterized in that, with regard to any of the firstthrough sixth features, a negative-pressure generation mechanism isprovided on the high-pressure fluid side of the seal area provided in amanner facing the low-pressure fluid side.

In addition, eighthly, the sliding component proposed by the presentinvention is characterized in that, with regard to the seventh features,the negative-pressure generation mechanism is a reversed Rayleigh stepmechanism.

According to these features, the fluid that would otherwise leak fromthe sealing face and fluid communication path toward the low-pressurefluid side flows into the negative-pressure generation mechanism and isdischarged toward the high-pressure fluid side via the fluidcommunication path, which further reduces the leakage of fluid.

In addition, ninthly, the sliding component proposed by the presentinvention is characterized in that, with regard to any of the firstthrough sixth features, a spiral groove for discharging fluid isprovided on the high-pressure fluid side of the seal area provided in amanner facing the low-pressure fluid side.

According to these features, the fluid that would otherwise leak fromthe sealing face and fluid communication path toward the low-pressurefluid side is discharged toward the high-pressure fluid side by thespiral groove, which further reduces the leakage of fluid.

In addition, tenthly, the sliding component proposed by the presentinvention is characterized in that, with regard to any of the firstthrough ninth features, the other sealing face is provided with a spiralgroove for discharging fluid, which groove opens toward thehigh-pressure fluid side while being isolated from the low-pressurefluid side by the seal area.

According to these features, the fluid that would otherwise leak fromthe high-pressure fluid side toward the low-pressure fluid side can befurther reduced. Furthermore, the spiral groove is isolated from thelow-pressure fluid side by the seal area, which prevents the fluid fromleaking in a stationary state.

In addition, eleventhly, the sliding component proposed by the presentinvention is characterized in that, with regard to any of the firstthrough fifth features, dimples that assist in the generation of dynamicpressure are provided all around the one sealing face.

According to these features, the dimples function as dynamic-pressureassisting grooves to lower the speed at the fluid lubrication transitionpoint of the sealing face, thereby achieving lower torque across allrotational speed regions.

In addition, twelfthly, the sliding component proposed by the presentinvention is characterized in that, with regard to any of the firstthrough fifth features, a radial overhang connecting to the land isprovided in at least one location of the seal area in thecircumferential direction, while pumping grooves are provided atpositions spaced from the seal area on the low-pressure fluid side inthe radial direction, wherein the pumping grooves extend in thecircumferential direction and their ends are positioned near theconnection parts of the overhang and land.

According to these features, increase in torque can be suppressed evenin high rotational speed regions.

In addition, thirteenthly, the sliding component proposed by the presentinvention is characterized in that, with regard to any of the firstthrough fifth features, each land has a different length in the radialdirection.

According to these features, the leakage rate and torque can be reduced.

In addition, fourteenthly, the sliding component proposed by the presentinvention is characterized in that, with regard to any of the firstthrough thirteenth features, the one sealing face is givenhydrophilizing treatment.

According to these features, lower torque can be achieved on the sealingface.

Advantageous Effects of Invention

The present invention achieves excellent effects as described below.

(1) The fluid entering the fluid communication path extending in theradial direction from the high-pressure fluid side is pressurized bymeans of the dynamic-pressure generating action of the land and positivepressure is generated, and consequently the space between the sealingfaces is widened and the lubrication of the sealing faces improves as aresult. As this happens, impurities contained in the fluid circulate inthe fluid communication path and eventually are discharged toward thehigh-pressure fluid side by centrifugal forces, instead of damaging thesealing faces, and therefore the life of the sliding component can beextended significantly. In addition, impurities do not deposit on thesealing faces to widen the space between the sealing faces, which inturn leads to greater sealing function.

(2) The land is provided at multiple locations at an equal pitch in thecircumferential direction, and accordingly required dynamic pressure isgenerated uniformly in the circumferential direction to improve thelubrication of the sealing face as a whole, while allowing theimpurities contained in the fluid to be discharged without fail.

(3) A feature resides in that the land has an approximately U-shapedprofile and is positioned in such a way that the top of the approximateU shape faces the high-pressure fluid side.

Accordingly to the feature, the presence of the dynamic-pressuregeneration area being elongated in the radial direction improveslubrication and reduces friction. Also, the fluid communication pathextending in the radial direction communicates with the fluidcommunication path extending in the circumferential direction along asmooth arc, which allows the impurities contained in the fluid to bedischarged without being stagnated in the middle and depositing. As aresult, the sealing face is not damaged and this prevents the sealingface from corroding.

(4) The land has a quadrilateral profile and is positioned in such a waythat one corner of the quadrilateral faces the high-pressure fluid side,and accordingly the fluid communication path has a wide entrance facingthe high-pressure fluid side and narrows toward the low-pressure fluidside after the entrance and then widens again near the fluidcommunication path extending in the circumferential direction, and thisallows the impurities contained in the fluid to be discharged further.

(5) The land has a profile corresponding to multiple circles arranged inthe radial direction, and accordingly a seal structure suitable forthrust bearings can be provided and the impurities contained in thefluid can be discharged efficiently toward the high-pressure fluid side.

(6) The fluid communication path is provided with a spiral groove fordischarging fluid, and accordingly the fluid entering the fluidcommunication path is biased toward the high-pressure fluid side by thespiral groove for discharging fluid, and therefore the impuritiescontained in the fluid are discharged further toward the high-pressurefluid side by centrifugal forces and the biasing force from the spiralgroove.

(7) A negative-pressure generation mechanism is provided on thehigh-pressure fluid side of the seal area provided in a manner facingthe low-pressure fluid side, and accordingly the fluid that wouldotherwise leak from the sealing face and fluid communication path towardthe low-pressure fluid side flows into the negative-pressure generationmechanism and is discharged toward the high-pressure fluid side via thefluid communication path, which reduces the leakage of fluid further.

(8) A spiral groove for discharging fluid is provided on thehigh-pressure fluid side of the seal area provided in a manner facingthe low-pressure fluid side, and accordingly the fluid that wouldotherwise leak from the sealing face and fluid communication path towardthe low-pressure fluid side is discharged toward the high-pressure fluidside by the spiral groove, which reduces the leakage of fluid further.

(9) The other sealing face is provided with a spiral groove fordischarging fluid that opens toward the high-pressure fluid side whilebeing isolated from the low-pressure fluid side by the seal area, andaccordingly the fluid that would otherwise leak from the high-pressurefluid side toward the low-pressure fluid side can be reduced further.Furthermore, the spiral groove is isolated from the low-pressure fluidside by the seal area, which prevents the fluid from leaking in astationary state.

(10) Dimples that assist in the generation of dynamic pressure areprovided all around the one sealing face, and accordingly the dimplesfunction as dynamic-pressure assisting grooves to lower the speed at thefluid lubrication transition point of the sealing face, therebyachieving lower torque across all rotational speed regions.

(11) A radial overhang connecting to the land is provided in at leastone location of the seal area in the circumferential direction, whilepumping grooves are provided at positions spaced from the low-pressurefluid side of the seal area in the radial direction, wherein the pumpinggrooves extend in the circumferential direction and their ends arepositioned near the connection parts of the overhang and land, andaccordingly increase in torque can be suppressed even in high rotationalspeed regions.

(12) Each land has a different length in the radial direction, andaccordingly the leakage rate and torque can be reduced.

(13) The one sealing face is given hydrophilizing treatment, andaccordingly lower torque can be achieved on the sealing face.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal section view showing an example of a mechanicalseal as the sliding component pertaining to Example 1 of the presentinvention.

FIG. 2 shows the sealing face of the sliding component pertaining toExample 1 of the present invention.

FIG. 3 shows the sealing face of the sliding component pertaining toExample 2 of the present invention.

FIG. 4 shows the sealing face of the sliding component pertaining toExample 3 of the present invention.

FIG. 5 shows the sealing face of the sliding component pertaining toExample 4 of the present invention.

FIG. 6 shows the sealing face of the sliding component pertaining toExample 5 of the present invention.

FIG. 7 shows the sealing face of the sliding component pertaining toExample 6 of the present invention.

FIG. 8 shows the sealing face of the sliding component pertaining toExample 7 of the present invention.

FIG. 9 (a) shows the sealing face of the sliding component pertaining toExample 8 of the present invention, while (b) shows the torque testresult of the sliding component.

FIG. 10 shows the sealing face of the sliding component pertaining toExample 9 of the present invention.

FIG. 11 shows the test results of the sliding component pertaining toExample 9, where (a) shows the torque test result and (b) shows the leakcheck test result.

FIG. 12 shows the sealing face of the sliding component pertaining toExample 10 of the present invention.

FIG. 13 shows the test results of the sliding component pertaining toExample 10, where (a) shows the torque test result and (b) shows theleak check test result.

FIG. 14 shows the test results of the sliding component pertaining toExample 11, where (a) and (b) show the torque test results, while (c)shows the comparison of torque test results when the flat sealing faceis given and not given hydrophilizing treatment.

FIG. 15 is a drawing explaining prior art.

DESCRIPTION OF EMBODIMENTS

Modes for carrying out the present invention are explained below basedon examples by referring to the drawings. Note, however, that thedimensions, materials, shapes, relative positions of components, etc.stated in these examples are not intended to limit the scope of thepresent invention to such dimensions, materials, shapes, and relativepositions, unless expressly stated otherwise.

Example 1

The sliding component pertaining to Example 1 of the present inventionis explained by referring to FIGS. 1 and 2.

In this example, a mechanical seal, which is an example of a slidingcomponent, is explained. It should also be noted that, while the outerperiphery side of the sliding component constituting the mechanical sealis referred to as the high-pressure fluid side (sealed fluid side) andthe inner periphery side is referred to as the low-pressure fluid side(atmosphere side) in the explanation, the present invention is notlimited to the foregoing and it can also be applied when thehigh-pressure fluid side and low-pressure fluid side are reversed.

FIG. 1 is a longitudinal section view showing an example of a mechanicalseal of the inside type that seals the sealed fluid on the high-pressurefluid side that would otherwise leak from the outer periphery toward theinner periphery of the sealing face, wherein the mechanical sealcomprises: one sliding part which is a circular rotating ring 3 andprovided via a sleeve 2 on a rotating shaft 1 side that drives a pumpimpeller (not illustrated) on the high-pressure fluid side in a mannerrotatable together with the rotating shaft 1; and the other sliding partwhich is a circular stationary ring 5 and provided on a pump housing 4in a manner not rotating but movable in the axial direction; and slidingsurfaces S that have been lapped or otherwise finished to a mirrorsurface are caused to slide against each other while in contact by meansof a coiled wave spring 6 and bellows 7 that bias the stationary ring 5in the axial direction. In other words, this mechanical seal preventsthe sealed fluid from flowing out from the outer periphery of therotating shaft 1 toward the atmosphere side between the respectivesealing faces S of the rotating ring 3 and stationary ring 5.

FIG. 2 shows the sealing face of the sliding component pertaining toExample 1 of the present invention, and the example explained hereassumes that a pumping groove is formed on the sealing face of thestationary ring 5 in FIG. 1.

The same applies when a pumping groove is formed on the sealing face ofthe rotating ring 3.

In FIG. 2, the outer periphery side of the sealing face of thestationary ring 5 represents the high-pressure fluid side (sealed fluidside), while the inner periphery side represents the low-pressure fluidside, such as the atmosphere side, and the mating sealing face rotatesin the counterclockwise direction.

The sealing face of the stationary ring 5 is provided with a land 10 forgenerating dynamic pressure facing the high-pressure fluid side and aseal area 11 facing the low-pressure fluid side. The seal area 11 isconstituted by a smooth area of the sealing face and provides sealingaction. The land 10 and seal area 11 are positioned away from each otherin the radial direction. In addition, the areas of the sealing faceother than the land 10 and seal area 11 are formed lower than theseareas and these lower areas constitute fluid communication paths 12.

In FIG. 2, the land 10 is provided at multiple locations at an equalpitch in the circumferential direction, and the respective lands areaway from one another and independent. Then, a fluid communication path12 a extending in the radial direction is formed at multiple locationsbetween adjacent lands 10, 10 in a manner facing the high-pressure fluidside. Also, a fluid communication path 12 b extending in thecircumferential direction is formed between the land 10 and seal area11, and the multiple fluid communication paths 12 a extending in theradial direction communicate with one another via the fluidcommunication path 12 b extending in the circumferential direction. Thewidth of each land 10 in the circumferential direction, widths of thefluid communication path 12 a extending in the radial direction, andfluid communication path 12 b extending in the circumferentialdirection, and depths of these fluid communication paths 12 a, 12 b, areset to optimal values based on the relative speed of the sealing faces,viscosity of the sealed fluid, and so on. For example, the width of eachland 10 in the circumferential direction is set on the order ofmillimeters, and the widths of the fluid communication paths 12 a, 12 bare equal to or smaller than the width of the land 10 in thecircumferential direction. The face of each land 10 is roughly at thesame height as the seal area 11. In addition, the fluid communicationpath 12 a extending in the radial direction and fluid communication path12 b extending in the circumferential direction are set 10 nm to 1 μmlower than the seal area 11, for example. Preferably the depth of thefluid communication path 12 b is 1 μm or less, because if it is 1 μm ormore, high dynamic pressure generates during high-speed rotation and thespace between the sealing faces is widened excessively to cause leakage.

Now, if the rotating ring 3 rotates and the sealing faces S of therotating ring 3 and stationary ring 5 are caused to slide relative toeach other, the fluid entering the fluid communication path 12 aextending in the radial direction from the high-pressure fluid side ispressurized by means of the dynamic-pressure generating action of theland 10 and positive pressure is generated, and consequently the spacebetween the sealing faces S of the rotating ring 3 and stationary ring 5is widened and the lubrication of the sealing faces S improves as aresult. As this happens, impurities contained in the fluid circulate inthe fluid communication path 12 b in the circumferential direction andeventually are discharged toward the high-pressure fluid side bycentrifugal forces, instead of damaging the sealing faces. In addition,impurities do not deposit on the sealing faces to widen the spacebetween the sealing faces, and therefore the life of the slidingcomponent can be extended significantly.

In the case of FIG. 2, the land 10 has a U-shaped profile and ispositioned in such a way that the top of this U shape faces thehigh-pressure fluid side.

When the land 10 has a U-shaped profile, as is the case above, thepresence of the dynamic-pressure generation area being elongated in theradial direction improves the lubrication and reduces the friction.Also, the fluid communication path 12 a extending in the radialdirection communicates with the fluid communication path 12 b extendingin the circumferential direction along a smooth arc, which allows theimpurities contained in the fluid to be discharged without beingstagnated in the middle and depositing. As a result, the sealing face isnot damaged and this prevents the sealing face from corroding.

Example 2

The sliding component pertaining to Example 2 of the present inventionis explained by referring to FIG. 3.

In Example 2, the basic constitution is the same as in Example 1,although the profile of the land is different from that in Example 1,and therefore the same members referenced in Example 1 are denoted bythe same symbols used in Example 1 and duplicate explanations areomitted.

In FIG. 3, a land 15 has a profile being a variation of a U shape.

To be specific, the land 15 has a U-shaped profile whose top has anormal shape but whose bottom (part near the low-pressure fluid side) isinclined by approx. 15 to 60° so that it faces the direction oppositethe sliding direction of the mating sealing face. In a fluidcommunication path 16, therefore, a fluid communication path 16 aextending in the radial direction is bent in a doglegged shape towardthe upstream side.

Because the fluid communication path 16 a extending in the radialdirection is bent in a doglegged shape toward the upstream side, thegeneration of dynamic pressure by the fluid entering the fluidcommunication path 16 a extending in the radial direction, from thehigh-pressure fluid side, is improved further. And, even in this case,the fluid communication path 16 a extending in the radial directioncommunicates with a fluid communication path 16 b extending in thecircumferential direction along a smooth arc, which allows theimpurities contained in the fluid to be discharged without beingstagnated in the middle.

Under the present invention, the U shape and all variations of U shapeare collectively referred to as “approximate U shape.”

Example 3

The sliding component pertaining to Example 3 of the present inventionis explained by referring to FIG. 4.

In Example 3, the basic constitution is the same as in Example 1,although the profile of the land is different from that in Example 1,and therefore the same members referenced in Example 1 are denoted bythe same symbols used in Example 1 and duplicate explanations areomitted.

In FIG. 4, a land 20 has a quadrilateral profile and is positioned insuch a way that one corner 20 a of the quadrilateral faces thehigh-pressure fluid side. In addition, an opposing corner 20 b of thecorner 20 a facing the high-pressure fluid side faces the low-pressurefluid side. Furthermore, a diagonal line 20 c connecting the corner 20 aand opposing corner 20 b is longer than the diagonal lines connectingthe other corners and inclined from the low-pressure fluid side towardthe high-pressure fluid side in the rotating direction of the matingsealing face. In a fluid communication path 21, a fluid communicationpath 21 a defined in the radial direction has a wide entrance facing thehigh-pressure fluid side, and narrows toward the low-pressure fluid sideafter the entrance and then widens again as it nears a fluidcommunication path 21 b defined in the circumferential direction.

With the sliding component in Example 3, the fluid communication path 21a extending in the radial direction narrows toward the low-pressurefluid side and then widens again near the fluid communication path 21 bin the circumferential direction, and accordingly impurities containedin the fluid flow easily into the fluid communication path 21 bextending in the circumferential direction and are discharged further.

Example 4

The sliding component pertaining to Example 4 of the present inventionis explained by referring to FIG. 5.

In Example 4, the basic constitution is the same as in Example 1,although the profile of the land is different from that in Example 1,and therefore the same members referenced in Example 1 are denoted bythe same symbols used in Example 1 and duplicate explanations areomitted.

In FIG. 5, a land 25 has a profile corresponding to multiple circlesarranged in the radial direction.

A circle 25 a on the high-pressure fluid side is positioned near theouter periphery surface of the sealing face. On the other hand, a circle25 b on the low-pressure fluid side is positioned along the seal area 11with a space left in between.

The sliding component in Example 4 represents a seal structure suitablefor thrust bearings, where impurities contained in the fluid entering afluid communication path 26 a extending in the radial directioncirculate in the circumferential direction via a fluid communicationpath 26 b extending in the circumferential direction and are dischargedtoward the high-pressure fluid side by centrifugal forces.

Example 5

The sliding component pertaining to Example 5 of the present inventionis explained by referring to FIG. 6.

In Example 5, the constitution is the same as in Example 1, except thata spiral groove for discharging fluid is added in the fluidcommunication path, which is different from Example 1, and therefore thesame members referenced in Example 1 are denoted by the same symbolsused in Example 1 and duplicate explanations are omitted.

In FIG. 6, a spiral groove 13 for discharging fluid is provided in thefluid communication path 12. This spiral groove 13 is formed byproviding a spiral-shaped groove on the surface of the fluidcommunication path 12, where, in FIG. 6, the spiral groove 13 isinclined from the low-pressure fluid side (inner periphery side) towardthe high-pressure fluid side (outer periphery side) in the rotatingdirection of the mating sealing face.

With the sliding component in Example 5, where the spiral groove 13 fordischarging fluid is provided in the fluid communication path 12, thefluid enters the fluid communication path 12 b extending in thecircumferential direction, from the fluid communication path 12 aextending in the radial direction, to be biased toward the high-pressurefluid side, in the fluid communication path 12, by the spiral groove 13for discharging fluid. As a result, impurities contained in the fluidare discharged more easily toward the high-pressure fluid side bycentrifugal forces and the biasing force from the spiral groove 13.

Example 6

The sliding component pertaining to Example 6 of the present inventionis explained by referring to FIG. 7.

In Example 6, the constitution is the same as in Example 1, except thata negative-pressure generation mechanism or spiral groove fordischarging fluid is provided on the high-pressure fluid side of theseal area, which is different from Example 1, and therefore the samemembers referenced in Example 1 are denoted by the same symbols used inExample 1 and duplicate explanations are omitted.

In FIG. 7(a), a negative-pressure generation mechanism 30 is provided onthe high-pressure fluid side of the seal area 11 provided on thelow-pressure fluid side. In the case of FIG. 7, the negative-pressuregeneration mechanism 30 is constituted by a reversed Rayleigh stepmechanism. This reversed Rayleigh step mechanism has a groove 30 aformed on the seal area 11 and a reversed Rayleigh step 30 b on theupstream side of the groove 30 a, while the downstream side of thegroove 30 a is open to the fluid communication path 12 b extending inthe circumferential direction. Preferably the depth of the groove 30 ais the same as or slightly less than the depth of the fluidcommunication path 12 b in the circumferential direction. The reversedRayleigh step mechanism 30 is provided at multiple locations at an equalpitch in the circumferential direction.

With the sliding component in Example 6, where the negative-pressuregeneration mechanism 30 is provided on the high-pressure fluid side ofthe seal area 11 provided on the low-pressure fluid side, the fluid thatwould otherwise leak from the sealing face and fluid communication path12 toward the low-pressure fluid side flows into the negative-pressuregeneration mechanism 30 and is discharged toward the high-pressure fluidside via the fluid communication path 12, and leakage of fluid can bereduced as a result.

While the negative-pressure generation mechanism 30 is provided on thehigh-pressure fluid side of the seal area 11 provided on thelow-pressure fluid side in FIG. 7(a), a spiral groove 13 for dischargingfluid may be provided in place of the negative-pressure generationmechanism, as shown in FIG. 7(b).

Example 7

The sliding component pertaining to Example 7 of the present inventionis explained by referring to FIG. 8.

In Example 7, the constitution of the one sealing face is the same as inExample 1, although a spiral groove for discharging fluid is provided onthe other sealing face, which is different from Example 1, and thereforethe same members referenced in Example 1 are denoted by the same symbolsused in Example 1 and duplicate explanations are omitted.

In FIG. 8, FIG. 8(a) shows the sealing face of a stationary ring 5,while FIG. 8(b) shows the sealing face of a rotating ring 3.

As shown in FIG. 8(b), the sealing face of the rotating ring 3 isprovided, across its entire surface, with spiral grooves 14 fordischarging fluid, which grooves are open to the high-pressure fluidside but isolated from the low-pressure fluid side by the seal area 11.

With the sliding component in Example 7, the sealing face of therotating ring 3, or specifically the other sealing face, is providedwith spiral grooves for discharging fluid and therefore the fluid thatwould otherwise leak from the high-pressure fluid side toward thelow-pressure fluid side can be reduced further. In addition, the spiralgroove 14 is isolated from the low-pressure fluid side by the seal area11, which prevents the fluid from leaking in a stationary state.

Example 8

The sliding component pertaining to Example 8 of the present inventionis explained by referring to FIG. 9.

In Example 8, the constitution is the same as in Example 1, except thatdimples that assist in the generation of dynamic pressure are providedall around on the one sealing face, which is different from Example 1,and therefore the same members referenced in Example 1 are denoted bythe same symbols used in Example 1 and duplicate explanations areomitted.

In FIG. 9(a), dimples 30 that assist in the generation of dynamicpressure are provided all around the sealing face of the stationary ring5, or specifically one sealing face on which a U-shaped land forgenerating dynamic pressure, seal area 11, and fluid communication path12 are provided.

The dimples 30 are provided to the extent that a porosity (area ratio)of approx. 5% is achieved, for example, but the porosity may be higheror lower. Also, the dimples 30 may be extremely shallow with a depth of100 nm or so, for example, but the depth is not limited in any specificway.

It should be noted that, while dimples 30 are provided all around thesealing face across its entire surface in FIG. 9(a), they need not bealways provided in the fluid communication paths 12 (12 a, 12 b)representing areas lower than the land 10 and seal area 11.

The U shape or other shape in which the land 10 for generating dynamicpressure is provided affects the torque characteristics of the slidingcomponent by causing the sealing face to undulate, sag, etc., and, inparticular, sagging of the sealing face from the inner periphery sidetoward the outer periphery side of the sealing face in the radialdirection suppresses the dynamic pressure effect and moves the fluidlubrication transition point of the sealing face toward the high speedside. When many extremely shallow dimples 30 are provided, however, atleast in the land 10 of the sealing face as well as all around the sealarea 11, these dimples 30 function as dynamic-pressure assisting groovesto lower the speed at the fluid lubrication transition point of thesealing face.

FIG. 9(b) shows the torque test results of the sliding component inExample 8 where dimples were provided on the sealing face and a slidingpart where no dimples were provided, and in the test conducted byvarying the rotational speed from 0 to 1000 and back to 0 rpm, thetorque was consistently low in virtually all rotational speed regionswith the sliding component in Example 8 where dimples were provided onthe sealing face, but it was high at rotational speeds in a range from 0to over 600 rpm with the sliding part where no dimples were provided.

In other words, the sliding component in Example 8 where dimples wereprovided on the sealing face could lower the speed at the fluidlubrication transition point and achieve lower torque across allrotating speed regions.

Example 9

The sliding component pertaining to Example 9 of the present inventionis explained by referring to FIG. 10.

In Example 9, the constitution is the same as in Example 1, except thatpumping grooves are provided on one sealing face in a manner extendingin the circumferential direction at positions spaced from thelow-pressure fluid side of the seal area in the radial direction, whichis different from Example 1, and therefore the same members referencedin Example 1 are denoted by the same symbols used in Example 1 andduplicate explanations are omitted.

When FIG. 10 is referenced, the sealing face of the stationary ring 5,or specifically one sealing face where the U-shaped land 10 forgenerating dynamic pressure, seal area 11, and fluid communication path12 are provided, is such that the seal area 11 has radial overhangs 11 aconnected to the land 10 at four equally distributed positions in thecircumferential direction, with pumping grooves 32 provided from thelow-pressure fluid side of the seal area 11 at four positions equallyspaced in the radial direction. The pumping grooves 32 extend in thecircumferential direction with their ends 32 a, 32 a bent outward in theradial direction, and are positioned near the connection part of theoverhangs 11 a and land 10.

While the overhang 11 a on the seal area 11 and pumping grooves areprovided at four equally distributed positions in the circumferentialdirection in FIG. 10, this is not the only possibility and it sufficesto provide at least one. Also, the sliding component in FIG. 10 can beused in applications where it rotates in either direction because thepumping grooves 32 have a laterally symmetrical shape.

When FIG. 10(b) showing the section A-A of FIG. 10(a) is referenced, thepumping grooves 32 have an approximately rectangular section shape andare set shallower than the fluid communication path 12, for example.

As the sealing face of the stationary ring 5 slides relative to themating sealing face, cavitation occurs in the pumping groove 32 and thiscavitation causes the fluid on the seal area 11 on the low-pressurefluid side (inner periphery side) to be suctioned into the pumpinggroove 32. The fluid that has been suctioned into the pumping groove 32generates dynamic pressure on the outer periphery side.

As described above, the formation of the pumping groove 32 causes thefluid that would otherwise leak toward the low-pressure fluid side to betransported toward the high-pressure fluid side (outer periphery side)to reduce the leakage rate, while also reducing the torque because theshear resistance decreases due to cavitation.

It should be noted that, while the pumping groove 32 is set shallowerthan the fluid communication path 12 in the example of FIG. 10, thegroove depth is not limited to the foregoing and the groove may be setdeeper than the fluid communication path 12.

FIG. 11(a) shows the torque test results of the sliding componentpertaining to Example 9 where pumping grooves were provided on thesealing face and no pumping grooves were provided on a sliding part, andin the test conducted by varying the rotational speed from 0 to 1000 andback to 0 rpm, the torque of the sliding part where no pumping grooveswere provided was high in virtually all rotational speed regions, andparticularly in the region of approx. 500 rpm and higher rotationalspeeds, it was greater than the torque of the sliding componentpertaining to Example 9 where pumping grooves were provided.

In other words, the sliding component pertaining to Example 9 wherepumping grooves were provided on the sealing face can suppress increasein torque even in regions of high rotational speeds.

FIG. 11(b) shows the leak check test results of the sliding component:pertaining to Example 9 where pumping grooves were provided on thesealing face and no pumping grooves were provided on a sliding part, andin the test conducted under the conditions of 8000 rpm in rotationalspeed and 015 MPaG in pressure, the leakage rate increased continuouslyafter the start of test with the sliding part where no pumping grooveswere provided on the sealing face, while the leakage rate was still assmall as 3 ml even after an elapse of 70 hours with the slidingcomponent pertaining to Example 9 where pumping grooves were provided onthe sealing face.

In other words, with the sliding component pertaining to Example 9 wherepumping grooves were provided on the sealing face, the leakage rate didnot increase over time.

Example 10

The sliding component pertaining to Example 10 of the present inventionis explained by referring to FIG. 12.

In Example 10, the constitution is the same as in Example 1, except thatthe multiple lands for generating dynamic pressure as provided in thecircumferential direction have different lengths in the radialdirection, which is different from Example 1, and therefore the samemembers referenced in Example 1 are denoted by the same symbols used inExample 1 and duplicate explanations are omitted.

When FIG. 12 is referenced, the multiple U-shaped lands 10 forgenerating dynamic pressure as provided in the circumferential directionare such that multiple lands 10 of different lengths in the radialdirection are arranged at an equal pitch in a cyclical manner.

To be specific, the multiple lands 10 are constituted by five types oflands having different lengths in the radial direction, which arearranged, for example, in the order from longest to shortest-from thelongest land 10-1 in the radial direction to the shortest land 10-5 inthe radial direction-in the rotating direction of the mating sealingface, and then in the order of shortest to longest-from the shortestland 10-5 in the radial direction to the longest land 10-1 in the radialdirection-in the rotating direction of the mating sealing face, and thisis repeated in the circumferential direction.

In the case of FIG. 12, while the multiple lands 10 are constituted byfive types of lands of different lengths in the radial direction, thenumber of types is not limited to five, so long as it is two or greater,for example. In addition, in FIG. 12, the structures are laterallysymmetrical and thus can be used in applications where it rotates ineither direction.

When the sealing face of the stationary ring 5 slides relative to themating sealing face, cavitation occurs from downstream of the longerlands in the radial direction, while cavitation also occurs in the innerperiphery parts of the shorter lands in the radial direction, as shownby hatching in the enlarged view of FIG. 12. If lands 10 of differentlengths in the radial direction are arranged in the circumferentialdirection (this arrangement may be hereinafter referred to as“long-and-short U shape”), the area where cavitation occurs becomeswider compared to when lands of a constant length in the radialdirection are arranged in the circumferential direction by equal numbers(this arrangement may be hereinafter referred to as “single-length Ushape”), and consequently the leakage rate and torque can be reduced.

FIG. 13(a) shows the torque test results of the sliding componentpertaining to Example 10 representing the long-and-short U shape and asliding component representing the single-length U shape, and in thetest conducted by varying the rotational speed from 0 to 1000 and backto 0 rpm, the torque of the sliding component representing thesingle-length U shape is greater in virtually all rotational speedregions, and particularly in the region of 500 rpm and higher rotationalspeeds, it is greater than the torque of the sliding componentpertaining to Example 10 representing the long-and-short U shape.

In other words, the sliding component pertaining to Example 10representing the long-and-short U shape can suppress increase in torqueeven in regions of high rotational speeds.

FIG. 13(b) shows the leakage check test results of the sliding componentpertaining to Example 10 representing the long-and-short U shape and asliding component representing the single-length U shape, and in thetest conducted under the conditions of 8000 rpm in rotational speed and015 MPaG in pressure, the leakage rate increased continuously after thestart of test with the sliding component representing the single-lengthU shape, while the leakage rate was still as small as 3 ml even after anelapse of 70 hours with the sliding component pertaining to Example 10representing the long-and-short U shape.

In other words, with the sliding component pertaining to Example 10representing the long-and-short U shape, the leakage rate did notincrease over time.

Example 11

The sliding component pertaining to Example 11 of the present inventionis explained by referring to FIG. 14.

In Example 11, the constitution is the same as in Example 1, except thatthe sealing face was given hydrophilizing treatment, which is differentfrom Example 1.

The study conducted by the inventor of the present application forpatent revealed that, when the sliding component of Example 1 as shownin FIG. 2 was produced using a sample free from pores, etc., the sealingface could not retain liquid film and the torque tended to increaseunder high-temperature, high-speed conditions, but when it was producedusing a sample whose sealing face had been hydrophilized, the sealingface could retain liquid film and exhibited fluid lubrication propertyeven under high-temperature, high-speed conditions.

The method for the hydrophilizing treatment of the sealing face is notlimited in any way, and examples include irradiating plasma onto thesealing face. Plasma irradiation can be implemented in several differentways, such as oxygen plasma irradiation, for example.

FIGS. 14(a) and (b) show the torque test results of the slidingcomponent pertaining to Example 11.

When FIG. 14(a) is referenced that assumes a fluid temperature of 60° C.in the test conducted by varying the rotational speed from 0 to 1000 andback to 0 rpm, the “Untreated” sample whose sealing face was nothydrophilized presented greater torque at rotational speeds of 6000 rpmand higher compared to the “Hydrophilized” sample whose sealing face washydrophilized.

Also when FIG. 14(b) is referenced, using a fluid temperature of 120°C., the “Untreated” sample whose sealing face was not hydrophilizedpresented greater torque in virtually all rotational speed regionscompared to the “Hydrophilized” sample whose sealing face washydrophilized, and the torque of the former increased notably atrotational speeds of approx. 3000 rpm and higher.

FIG. 14(c) shows the torque test results of samples whose flat sealingface was hydrophilized and not hydrophilized.

As shown in FIGS. 14(a) and (b), the torque-lowering effect was observedwhen the sealing face provided with a U-shaped land 10 for generatingdynamic pressure, seal area 11, and fluid communication path 12, asshown in Example 1, was hydrophilized.

As shown in FIG. 14(c), however, the torque-lowering effect was notachieved when the flat sealing face not provided with a U-shaped landfor generating dynamic pressure, etc., as shown in Example 1, washydrophilized.

The above test results indicate that a specific effect manifestsmarkedly when a sealing face provided with a U-shaped land 10 forgenerating dynamic pressure, seal area 11, and fluid communication path12, as shown in Example 1, is hydrophilized.

The foregoing explained the examples of the present invention using thedrawings, but specific constitutions are not limited to these examplesand other modifications and additions are also included in the scope ofthe present invention so long as they do not deviate from the key pointsof the present invention.

For example, while the aforementioned examples primarily explained caseswhere the sliding part was used for either the rotating seal ring orstationary seal ring in a pair of rings constituting a mechanical sealdevice, the sliding part can also be used as a bearing that slidesagainst a rotating shaft while sealing lubricating oil on one side of acylindrical sealing face in the axial direction.

Additionally, while the aforementioned examples explained the so-calledinside type characterized by the presence of high-pressure sealed fluidon the outer periphery side, for example, it goes without saying thatthe present invention can also be applied to the outside typecharacterized by the presence of high-pressure fluid on the innerperiphery side.

In this case, the position of the land for generating dynamic pressureand that of the seal area are reversed in the radial direction.

Additionally, while the aforementioned examples explained cases wherethe land for generating dynamic pressure, fluid communication path, andseal area were provided on the sealing face of the stationary ring, forexample, this is not the only possibility and the land for generatingdynamic pressure, fluid communication path, and seal area can also beprovided on the sealing face of the rotating ring.

REFERENCE SIGNS LIST

-   -   1 Rotating shaft    -   2 Sleeve    -   3 Rotating ring    -   4 Housing    -   5 Stationary ring    -   6 Coiled wave spring    -   7 Bellows    -   10 Land    -   11 Seal area    -   12 Fluid communication path    -   12 a Fluid communication path extending in the radial direction    -   12 b Fluid communication path extending in the circumferential        direction    -   13 Spiral groove    -   14 Spiral groove    -   15 Land    -   16 Fluid communication path    -   16 b Fluid communication path extending in the circumferential        direction    -   20 Land    -   21 Fluid communication path    -   21 a Fluid communication path extending in the radial direction    -   21 b Fluid communication path extending in the circumferential        direction    -   25 Land    -   26 a Fluid communication path extending in the radial direction    -   26 b Fluid communication path extending in the circumferential        direction    -   30 Dimple    -   32 Pumping groove

The invention claimed is:
 1. A sliding component provided with a mechanism to generate dynamic pressure by means of relative sliding of a pair of sealing faces of the sliding part, the pair of sealing faces being constituted by a first sealing face and a second sealing face, wherein the first sealing face is provided with multiple lands separately aligned in a circumferential direction for generating dynamic pressure and facing a high-pressure fluid side and, an annular seal area separated from the lands and facing a low-pressure fluid side, wherein a part of the first sealing face other than the lands and the annular seal area is formed lower than the lands and the annular seal area to constitute a fluid communication path open to the high-pressure fluid side, wherein a plurality of grooves each including reversed Rayleigh steps for generating a negative pressure are provided on the high-pressure fluid side of the annular seal area so as to be aligned in the circumferential direction, wherein the plurality of grooves each has a first end positioned on an upstream side of a relative rotational direction of the second sealing face with respect to the first sealing face and a second end positioned on a downstream side of the relative rotational direction of the second sealing face with respect to the first sealing face, the reversed Rayleigh step being formed at the first end of each of the plurality of grooves, and wherein the first end of each of the plurality of grooves has a dead-end structure, and each of the plurality of grooves communicates with the fluid communication path only through each of radial grooves connected to the second end of each of the plurality of grooves wherein a depth of the first end is same or slightly less than a depth of the fluid communication path.
 2. A sliding component according to claim 1, wherein the fluid communication path is constituted by multiple radial fluid communication paths each of which separates the adjoining lands from each other, and a circumferential fluid communication path which separates the annular seal area from the lands.
 3. A sliding component according to claim 1, wherein the lands are arranged an equal pitch in the circumferential direction.
 4. A sliding component according to claim 1, wherein each of the lands has an approximately U-shaped profile and is positioned in such a way that a top of the approximate U shape faces the high-pressure fluid side. 